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Scientists predict rare 'hibernation' of sunspots
AFP



Scientists predict rare hibernation of sunspots AFP/File

by Kerry Sheridan – Tue Jun 14, 5:38 pm ET

WASHINGTON (AFP) – For years, scientists have been predicting the Sun
would by around 2012 move into solar maximum, a period of intense flares
and sunspot activity, but lately a curious calm has suggested quite the
opposite.

According to three studies released in the United States on Tuesday,
experts believe the familiar sunspot cycle may be shutting down and
heading toward a pattern of inactivity unseen since the 17th century.

The signs include a missing jet stream, fading spots, and slower activity
near the poles, said experts from the National Solar Observatory and Air
Force Research Laboratory.

"This is highly unusual and unexpected," said Frank Hill, associate
director of the NSO's Solar Synoptic Network, as the findings of the three
studies were presented at the annual meeting of the American Astronomical
Society's Solar Physics Division in Las Cruces, New Mexico.

"But the fact that three completely different views of the Sun point in
the same direction is a powerful indicator that the sunspot cycle may be
going into hibernation."

Solar activity tends to rise and fall every 11 years or so. The solar
maximum and solar minimum each mark about half the interval of the
magnetic pole reversal on the Sun, which happens every 22 years.

Hill said the current cycle, number 24, "may be the last normal one for
some time and the next one, cycle 25, may not happen for some time.

"This is important because the solar cycle causes space weather which
affects modern technology and may contribute to climate change," he told
reporters.

Experts are now probing whether this period of inactivity could be a
second Maunder Minimum, which was a 70-year period when hardly any
sunspots were observed between 1645-1715, a period known as the "Little
Ice Age."

"If we are right, this could be the last solar maximum we'll see for a few
decades. That would affect everything from space exploration to Earth's
climate," said Hill.

Solar flares and eruptions can send highly charged particles hurtling
toward Earth and interfere with satellite communications, GPS systems and
even airline controls.

Geomagnetic forces have been known to occasionally garble the world's
modern gadgetry, and warnings were issued as recently as last week when a
moderate solar flare sent a coronal mass ejection in the Earth's
direction.

The temperature change associated with any reduction in sunspot activity
would likely be minimal and may not be enough to offset the impact of
greenhouse gases on global warming, according to scientists who have
published recent papers on the topic.

"Recent solar 11-year cycles are associated empirically with changes in
global surface temperature of 0.1 Celsius," said Judith Lean, a solar
physicist with the US Naval Research Laboratory.

If the cycle were to stop or slow down, the small fluctuation in
temperature would do the same, eliminating the slightly cooler effect of a
solar minimum compared to the warmer solar maximum. The phenomenon was
witnessed during the descending phase of the last solar cycle.

This "cancelled part of the greenhouse gas warming of the period
2000-2008, causing the net global surface temperature to remain
approximately flat -- and leading to the big debate of why the Earth
hadn't (been) warming in the past decade," Lean, who was not involved in
the three studies presented, said in an email to AFP.

A study in the March 2010 issue of Geophysical Research Letters explored
what effect an extended solar minimum might have, and found no more than a
0.3 Celsius dip by 2100 compared to normal solar fluctuations.

"A new Maunder-type solar activity minimum cannot offset the global
warming caused by human greenhouse gas emissions," wrote authors Georg
Feulner and Stefan Rahmstorf, noting that forecasts by the
Intergovernmental Panel on Climate Change have found a range of 3.7
Celsius to 4.5 Celsius rise by this century's end compared to the latter
half of the 20th century.

"Moreover, any offset of global warming due to a grand minimum of solar
activity would be merely a temporary effect, since the distinct solar
minima during the last millennium typically lasted for only several
decades or a century at most."